Although drilling machinery for mines is well known in the prior art, because of very limited overhead space in coal mines it has been difficult to develop acceptable drilling equipment for placing explosives on both bottom and top of the tunnel facing parallel to the floor and roof as required to blast away the tunnel facing for removal of the facing in a pattern extending the mine tunnel shaft walls substantially in the same dimension without manual working, cutting or shaping of residual layers. This is in part because the placement of explosive charges such as dynamite sticks requires drilled holes up to about ten feet in depth located at special angles and positions in the mine wall facing at the end of the mine tunnel and in particular in positions extending the floor and ceiling lines. Special equipment is required for coal mines where a shaft is about twenty feet (6.1 M) wide and may be as low as two feet (0.61 M) high. This leads to the necessity for hand drilling particularly to provide a clear extension of the tunnel at the mine face which need be accomplished by placing charges adjacent the roof and floor into the face.
Thus, it has been difficult for many prior equipments to maneuver into desired locations for drilling at various angles. The usual equipment is not even usable in coal mines because of the large size and limited space to work and cannot be used to drill at desired positions for example into the mine face level with the mine tunnel floor. This has occurred because of ruggedness and size with which the equipment has been built in the past, because of high profile carriages or associated mechanisms, and because of limitations in positioning imposed by particular mechanisms and construction features inherent in prior art machines.
It is therefore an object of this invention to simplify mine drilling equipment without reducing performance and to make it more adaptable for universal positioning within coal mine tunnels where head space is very limited to place drill holes adjacent the floor and ceiling and at any other desired angles and locations on the mine facings, walls or ceilings.
The following U.S. patents typically display such prior art equipment having the aforesaid problems.
V. H. Nixon--U.S. Pat. No. 3,078,932--provides an auger holding array that limits its positioning so that it cannot be used to drill holes adjacent to and parallel with the floors or walls of an existing tunnel. Thus, framework structure for holding the auger and operating mechanisms such as hydraulic cylinders are disposed between the auger and the floor or wall of a mine so that it is not feasible to drill a hole in the end wall of a mine tunnel adjacent to floor or sidewall level and parallel with it. Furthermore the mountings and chassis mount are not adaptable for use in coal mine shafts with a height under about six feet. Thus, the equipment is not versatile enough to lay the charges in positions required in coal mine tunnel positions.
In C. F. Ball--U.S. Pat. No. 2,586,773--Feb. 26, 1952--a manually positioned auger is swivel joint mounted to extend from a telescopic boom. Similarly C. F. Osgood--U.S. Pat. No. 2,334,576--Nov. 16, 1943 shows such a pivoted boom assembly. It is most important that there is developed by a rotating drill a significant rotary torque component which makes an auger difficult to place, direct and handle precisely. This type of assembly has no effective way to remove this undesirable torque from the delicate pivot assembly.
Thus the drill equipment must be large and heavy and need be manually directed and pivot clamps locked. In order to assist manual positioning a counterbalance is provided to help pivot a heavy drill boom assembly which has a motor, a feed mechanism and an auger all linearly disposed to swing from the pivot point. In coal mines with limited head room the manual placement of the drill at starting position is not feasible.
L. W. Ray et al.--U.S. Pat. No. 3,834,761--Sept. 10, 1974--is a type of carriage mounted low profile large diameter auger for removing coal from mines, but is not useful in positioning a drill bit at any desired location in a mine shaft facing.
J. C. Curtis--U.S. Pat. No. 2,217,674--Oct. 15, 1940; J. C. Curtis et al.--U.S. Pat. No. 2,316,672--Apr. 13, 1943; and J. C. Curtis--U.S. Pat. No. 2,657,017--Oct. 27, 1953--provide a carriage mounted drill reciprocally movable along a boom which is positionable in a swinging path by means of a hydraulic cylinder and lever linkage system. This type drill rig does not provide low profile operation and cannot for example drill holes in a low height coal mine tunnel face at the floor level because of required undercarriage for resting on the tunnel floor and the inability to position the bit contiguous to the floor.
All of this prior art is deficient in drilling operations at low profile in the coal mine environment without manual manipulation and placement of the drilling head to place charges exactly where necessary to extend the mine shaft without further cutting and shaping, namely among other locations to drill parallel to and adjacent the floor and ceiling.
In particular, if holes are desired in the walls of a mine tunnel at an acute angle to the walls, such as for the mounting of wall support braces, the prior art has not provided self contained rigs that could be maneuvered across the tunnel width and position the drill to drill the holes without manual assistance.